Process of nitrating alcohols



Patented Mar. 12,1946

PROCESS OF NITRATING ALCOHOL James Edward Lufkin, Woodbury, N. 3.,assignor to E. I. du Pont de Nemours & Company, Wilmington, Deb, acorporation of Delaware No Drawing. Application February 27, 1945,

Serial No. 580,080

7 Claims.

This invention relates to a process for preparing nitric esters ofaliphatic and cycloaliphatic alcohols and more particularly to anitration process whereby such nitric esters, particularly of secondaryand tertiary alcohols, are obtained in good yields and under conditionsfavoring the main reaction and elimination of side reactions.

Alkyl nitrates have been made in the past by the action of nitric acidor mixtures of sulfuric and nitric acids on aliphatic alcohols. In thecase of primary alcohols, the esterification has been carried outordinarily without a great deal of difliculty, When attempts have beenmade to prepare secondary alkyl nitrates, however, results have beenmuch less satisfactory and an undesirable formation of oxidation ratherthan esterification products has taken place.

An object of the present invention is a novel and improved method ofpreparing nitric esters of aliphatic alcohols, particularly of secondaryand tertiary alcohols. A further object is such a method whereby thenitration reaction is better controlled, and greatly improved yields ofthe desired product are obtained. A still further object is a method ofnitration of higher alcohols whereby oxidation reactions are largelyeliminated. Additional objects will be disclosed as the invention isdescribed more at length hereinafter.

I have found that the foregoing objects are accomplished, and thedisadvantages of the methods of the prior art overcome, when I react acompound taken from the group consisting of the secondary and tertiaryaliphatic alcohols with nitric acid in the presence of acetic anhydride.While varying strengths of nitric acid may be utilized, material of highstrength will desirably be used, preferably over 95% strength, asconcentration of nitric acid is more attractive economically than theuse of increased amounts of acetic anhydride.

The following examples will serve as specific embodiments of proceduresfollowed in carrying out my invention. It will be understood, however,that these are not to be taken as limiting the invention in any way.

Example I crude amyl nitrate product amounted to 1278 grams, a yield of93.0%, based on the weight of alcohol used. The product had a specificgravity of 0.99 and a boiling range of 144-150 C.

Example II Again 908 grams of secondary amyl alcohol was caused to reactin a similar manner with 796 grams of 98% nitric acid, the two materialsbeing caused to flow at proportionate rates in separate streams into1420 grams of acetic anhydride. The temperature was maintained between20 and 33 C. After separation, washing and drying, 1293 grams of crudeamyl nitrate was obtained, a yield of 94.2%. The product had a boilingrange between 139 and 150 C.

In the addition of reactants, 5% of the total nitric acid was introducedat the start and the reactants were added at such a rate that 5% more ofthe nitric than of the alcohol had been added at all times. Subsequentlyit was found that a 15% lead of nitric acid was desirable.

Example III Example IV Twenty-two grams of diethyl carbinol and 20.8grams of 98% nitric acid were caused to flow into 31.2 grams of aceticanhydride in the same manner as described in the previous examples, thetemperature being maintained at 18-22" C. The crude nitrate, afterdrowning, separation, washing and drying amounted to 27.3 grams, a yieldof 82.0%, The product had a specific gravity of 0.97 and a boiling pointof around 140 C.

Example V Fifty grams of methyl isobutyl carbinol and 39.3 grams of 98%nitric acid were added gradually and simultaneously to 64 grams ofacetic anhydride, the addition being such that always 5% more of thenitric acid had been introduced than of the alcohol. Cooling water wasused, and a nitration temperature of 7-10 C. was maintained. Thenitration mixture was allowed to cook for five minutes at the end of thefeeding.

The mixture was drowned in cold water and the oil layer separated andneutralized. The product amounted to 69.0 grams, a yield of 95.7%, basedon the alcohol used.

Example VI A small sample of tertiary amyl alcohol was reacted with 98%nitric acid in an acetic anhydride medium in the manner described in thepreceding examples. The nitrated compound was obtained after separationof the product. Attempts to nitrate this tertiary alcohol by means ormixed sulfuric and nitric acids resulted in instantaneous fume-oils,even when the temperature was lowered to -18 C.

In the foregoing examples nitric acid has been used at a strength of 98%HNOa. High strength nitric acid is highly desirable, for example aboveamount of acetic anhydride will be required than if weaker nitric wereused. I am not limited, however, to acid of the high strengths cited. Ingeneral, I prefer to use an excess of nitric acid over thattheoretically required for the complealcohol, various secondary andtertiary amyl alcohols, and higher straight and branched chain secondaryand tertiary alcohols.

In carrying out the process of the invention, I may, if desired, firstmix the alcohol and acetic anhydride, and then add the nitric acidthereto. Preferably, however, I add the nitric acid and the alcoholsimultaneously to the acetic anhydride. Better control of the reactionis thereby obtained and such a procedure is considered desirable fromthe safety viewpoint, as no intermediate formation of undesirablecompounds results by this preferred procedure. While the nitric acid andalcohol may be said to be added simultaneously, I find it desirable tointroduce a small percentage of the total nitric acid at the outset, forexample 5-15%, and maintain this lead throughout the addition period, sothat all times there is this excess of nitric acid present. While theexamples have shown the procedure to comprise the introduction of nitricacid and alcohol into acetic anhydride, the three ingredients may allbeadded simultaneously, with a Such compounds may be 95% strength, as thismeans" that a smaller controlled excess of acetic anhydride and nitricacid. A continuous process may be carried out in this manner.

The method of my invention is very advantageous, as it allows thepreparation of nitrated compounds that would otherwise be impossible, orattainable only with great difficulty. when various secondary alcoholshave been nitrated by means of a mixture of sulfuric and nitric acid,for example, sub-zero temperatures must be maintained ordecomposition orpolymerization of'the product takes place, with resultant low yields.The present process allows the use of temperatures of 0 to 50 C., forexample, and higher, with the attainment of excellent yields.

The invention has been described clearly in the foregoing. It will beunderstood, however, that many variations in details of procedure and"specific compounds treated may be introduced without departure from thescope of the invention; I intend to be limited, therefore, only by thefollowing claims.

I claim:

1. A process for preparing aliphatic and cycloaliphatic nitrates whichcomprises reacting a compound taken from the group consisting of thesecondary and tertiary aliphatic and cycloaliphatic alcohols with nitricacid in the presence of acetic anhydride.

2. A process for preparing aliphatic nitrates which comprises causing topass simultaneously into acetic anhydride nitric acid and a compoundtaken from the group consisting of the secondary and tertiary aliphaticand cycloaliphatic alcohols, and bringing about reaction therein,

3. The process of claim 2, in which secondary butyl alcohol is reactedwith nitric acid.

4. The process of claim 2, in which a secondary amyl alcohol is reactedwith nitric acid.

5. A process for preparing aliphatic nitrates which comprises causing topass simultaneously into acetic anhydride nitric acid of over strength,and a compound taken from the group consisting of the secondary andtertiary aliphatic and cycloaliphatic alcohols, and bringing aboutreaction therein,

6; The process of claim 5, in which an excess of nitric acid over thealcohol is maintained throughout the addition period.

7. A process for preparing aliphatic nitrates which comprises causing toflow in contact with one another and at predetermined rates aceticanhydride, nitric acid of over 95% strength and a compound taken fromthe group consisting of the secondary and tertiary aliphatic and cyclo-'aliphatic alcohols, and causing reaction to take place therebetween.

JAMES EDWARD LUFKIN.

